PRESSURE-VOLUME RELATIONSHIPS IN NON-REHYDRATED TISSUE AT VARIOUS WATER DEFICITS

The purpose of this paper is to examine a technique for estimating the weight at full saturation (W(s)) from pressure-volume (P-V) analysis of nonrehydrated plant tissue at various water deficits. Tissue samples are typically rehydrated prior to P-V analysis to determine W(s), necessary to calculate many tissue water parameters. However, several studies have indicated that artificial rehydration may significantly alter P-V relationships, such as the plateau effect, resulting in erroneous measurements of tissue elasticity and osmotic potentials. The results of this study suggest that linear regression of P-V data at and above the turgor loss point may be used to extrapolate W(s) from non-rehydrated samples at various moisture deficits, thus eliminating the plateau effect and other potential rehydration problems. Determination coefficients and standard errors of the Y-intercept indicated a strong linear relationship between tissue fresh weight and water potential (psi), and a high degree of predictability of W(s) in all but one of the species-treatment combinations evaluated in this study, despite predawn psi as low as - 1.0 MPa.